Surface plasmon resonance imaging of cell-substrate contacts with radially polarized beams

We demonstrate the proof-of-concept for surface plasmon resonance sensing and imaging via a virtual probe at the cell-substrate interface of a biological cell in aqueous media. The technique is based on the optical excitation by focused radially polarized beams of localized surface plasmons, which forms a virtual probe on the metal substrate. The intensity distribution at the back focal plane of the objective lens enables quantitative measurements to be made of the cell-substrate contact. The acquired data is then visualized in the form of a local refractive index map.